If using any of the Special Builds (i.e. Allbest, SDM, etc.) always try to use the language file the author provides for their particular build (usually available from the same download page where you obtained their build), rather than one of the generic ones from this Languages page, as these aren't often updated to reflect the myriad builds of CHDK. While they will still work for most of the basic menus and features, many of the newer builds have features (menu options) that aren't covered by the generic language files posted here.

Now your menu language should have changed.
Please note that the built-in font supports many codepages (=many different national characters (éèîäüß)), but there are few RBF fonts with other codepages than Win1251(Cyrillic). If you have chosen a RBF font but want to switch back to the original built-in font, just choose an "illegal" RBF font (Try to load a uBASIC script as a RBF font, for example). Tutorial how to make RBF fonts.

How to add a language

If you want to help translating the CHDK into your language, you can do so here: Start a new wiki page for your language, copy the english.lng in there and put some <pre> </pre> tags around it because it is preformatted text. Now you can start your translation.
Note: // is a commentary, \n is a line break.